[PATCH v10 16/27] KVM: x86: Add fault checks for guest CR4.CET setting

From: Yang Weijiang
Date: Mon Feb 19 2024 - 02:55:07 EST


Check potential faults for CR4.CET setting per Intel SDM requirements.
CET can be enabled if and only if CR0.WP == 1, i.e. setting CR4.CET ==
1 faults if CR0.WP == 0 and setting CR0.WP == 0 fails if CR4.CET == 1.

Co-developed-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
Reviewed-by: Chao Gao <chao.gao@xxxxxxxxx>
Reviewed-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
arch/x86/kvm/x86.c | 6 ++++++
1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 906307757159..5f5df7e38d3d 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1006,6 +1006,9 @@ int kvm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
(is_64_bit_mode(vcpu) || kvm_is_cr4_bit_set(vcpu, X86_CR4_PCIDE)))
return 1;

+ if (!(cr0 & X86_CR0_WP) && kvm_is_cr4_bit_set(vcpu, X86_CR4_CET))
+ return 1;
+
static_call(kvm_x86_set_cr0)(vcpu, cr0);

kvm_post_set_cr0(vcpu, old_cr0, cr0);
@@ -1217,6 +1220,9 @@ int kvm_set_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
return 1;
}

+ if ((cr4 & X86_CR4_CET) && !kvm_is_cr0_bit_set(vcpu, X86_CR0_WP))
+ return 1;
+
static_call(kvm_x86_set_cr4)(vcpu, cr4);

kvm_post_set_cr4(vcpu, old_cr4, cr4);
--
2.43.0